Surface Recombination Velocity from Photocurrent Measurements: Validation and Applications

Polignano, M. L.; Bellafiore, N.; Caputo, D.; Caricato, A. P.; Modelli, Alberto; Zonca, R.

doi:10.1149/1.1392687

Cited by 8 publications

(11 citation statements)

References 20 publications

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“…(B8) and (B11), respectively. Equations (6) and (12) are the fundamental equations of the present work. They allow us to calculate S for a given light excitation power and surface state density, with approximations listed in Appendix A.…”

Section: Knexpmentioning

confidence: 99%

“…4 After the early theoretical investigations which apply to the surface the Shockley Read Hall formalism (SRH) and obtain an expression of the surface recombination velocity S, 5 surface recombination has been extensively explored using photoconductivity, 6,7 surface photovoltage measurements, 8 scanning electron microscopy, 9 cathodoluminescence, 10 or photoluminescence [11][12][13] on a wide range of materials including GaAs, 12 Si, 14 InP, 15 GaN, 16 InN, 17 ZnSe, 18 and alloys. 19 However, the immense majority of these works rely on the usual hypothesis that S, as defined by the SRH formalism, is proportional to the surface density of states, and is a fundamental parameter for describing the surface electronic properties.…”

Section: Introductionmentioning

confidence: 99%

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Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

Cadiz

Paget

Rowe

et al. 2013

Journal of Applied Physics

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For n-and p-type semiconductors doped above the 10 16 cm À3 range, simple analytical expressions for the surface recombination velocity S have been obtained as a function of excitation power P and surface state density N T . These predictions are in excellent agreement with measurements on p-type GaAs films, using a novel polarized microluminescence technique. The effect on S of surface passivation is a combination of the changes of three factors, each of which depends on N T : (i) a power-independent factor which is inversely proportional to N T and (ii) two factors which reveal the effect of photovoltage and the shift of the electron surface quasi Fermi level, respectively. In the whole range of accessible excitation powers, these two factors play a significant role so that S always depends on power. Three physical regimes are outlined. In the first regime, illustrated experimentally by the oxidized GaAs surface, S depends on P as a power law of exponent determined by N T . A decrease of S such as the one induced by sulfide passivation is caused by a marginal decrease of N T . In a second regime, as illustrated by GaInP-encapsulated GaAs, because of the reduced value of S, the photoelectron concentration in the subsurface depletion layer can no longer be neglected. Thus, S À1 depends logarithmically on P and very weakly on surface state density. In a third regime, expected at extremely small values of P, the photovoltage is comparable to the thermal energy, and S increases with P and decreases with increasing N T . V C 2013 AIP Publishing LLC. [http://dx.

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Section: Knexpmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

Cadiz

Paget

Rowe

et al. 2013

Journal of Applied Physics

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“…In the electrolytical metal oxide semiconductor method [7,8] the wafer is contacted with conductive liquids on both sides. A laser beam scans the front surface and generates charge carriers diffusing to the back side of the wafer.…”

Section: Introductionmentioning

confidence: 99%

2D Mapping of Chemical and Field Effect Passivation of Al2O3 on Silicon Substrates

et al. 2015

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Fixed charge and interface defect densities are the critical material parameters for silicon surface passivation. These parameters are measured with high spatial resolution on 150 mm wafers using a novel method called 'BiasMDP'. In this method the effective carrier lifetime is determined by means of microwave detected photoconductivity while a bias voltage is applied to an electrode on top of the passivation layer. The measured carrier lifetime strongly reduces when the external bias voltage compensates the electric field of the fixed charges. Based on this minimum lifetime fixed charge and interface defect densities are calculated. The sensitivity of BiasMDP is demonstrated on a silicon wafer with Al 2 O 3 passivation, which is processed with thickness gradient. A continuous shift of flat band voltage is measured across the wafer. This shift linearly correlates with oxide thickness as predicted by theory. Furthermore, an Al 2 O 3 passivation stack with local HfO 2 interface layer is characterized. The 2D map of fixed charge density shows a variation between 0.5 x 10 12 cm -2 and 4.0 x 10 12 cm -2 of negative polarity. This inhomogeneity is attributed to the local presence or not presence of the HfO 2 interface layer. Finally, a wafer with local surface damage and inhomogeneous carrier lifetime distribution is measured with BiasMDP. The measurement shows that the inhomogeneity is caused by degradation of chemical passivation. BiasMDP is shown to be a powerful method for detecting inhomogeneities of passivation layers. BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer review by the scientific conference committee of SiliconPV 2015 under responsibility of PSE AG 92 Paul M. Jordan et al. / Energy Procedia 77 ( 2015 ) 91 -98

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“…Knowledge of surface recombination in semiconductors is crucial for bipolar nanoelectronics [1], in particular for high surface-to-volume ratio structures such as nanowires [2]. As a result surface recombination has been extensively explored using photoconductivity [3,4], surface photovoltage measurements [5], scanning electron microscopy [6], cathodoluminescence [7], or photoluminescence [8][9][10] on a wide range of materials including GaAs [9], Si [11], InP [12], GaN [13], InN [14], ZnSe [15] and alloys [16]. The immense majority of these works rely on the fact that the surface recombination velocity S is a fundamental parameter for describing the surface electronic properties [17].…”

Section: Introductionmentioning

confidence: 99%

Absence of an intrinsic value for the surface recombination velocity in doped semiconductors

Cadiz,

Paget,

Berkovits

et al. 2013

Preprint

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A self-consistent expression for the surface recombination velocity S and the surface Fermi level unpinning energy as a function of light excitation power (P ) is presented for n-and p-type semiconductors doped above the 10 16 cm −3 range. Measurements of S on p-type GaAs films using a novel polarized microluminescence technique are used to illustrate two limiting cases of the model. For a naturally oxidized surface S is described by a power law in P whereas for a passivated surface S −1 varies logarithmically with P . Furthermore, the variation in S with surface state density and bulk doping level is found to be the result of Fermi level unpinning rather than a change in the intrinsic surface recombination velocity. It is concluded that S depends on P throughout the experimentally accessible range of excitation powers and therefore that no instrinsic value can be determined. Previously reported values of S on a range of semiconducting materials are thus only valid for a specific excitation power.

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Surface Recombination Velocity from Photocurrent Measurements: Validation and Applications

Cited by 8 publications

References 20 publications

Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

2D Mapping of Chemical and Field Effect Passivation of Al2O3 on Silicon Substrates

Absence of an intrinsic value for the surface recombination velocity in doped semiconductors

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